In hypophysectomized dogs, renal arterial infusion of bradykinin, 5 mg/min, during a stable water diuresis increased cortical (CPAH) and non-cortical plasma flow (NCPF) and sodium excretion (UNaV). The increase in UNaV could be explained, in part, by an increase in delivery of proximal tubular fluid to the distal nephron CH2O plus Ccl/CIN and in part, by an inhibition of distal chloride reabsorption CH2O/CH2O plus Ccl. Inhibition of prostaglandin (PG) synthesis for three days significantly decreased free water formation CH2O/CIN and CH2O plus Ccl CIN such that net UNaV was not different. Infusion of bradykinin did not change CPAH but did increase NCPF, CH2O plus Ccl/CIN, inhibit CH2O/CH2O plus Ccl and increase UNaV as in control studies. Thus the effects of bradykinin on CPAH appear to be mediated by PG, whereas the effects of bradykinin on NCPF, tubular reabsorption of sodium appear to be PG-independent.